A comparison of 2 drilling techniques on the femoral tunnel for anterior cruciate ligament reconstruction.

PURPOSE This cadaveric study was undertaken to characterize the femoral tunnel geometry resulting from commonly used drilling techniques in anterior cruciate ligament reconstruction. METHODS We randomized 10 matched-pair cadaveric knees (20 knees) into 2 groups with right and left matched pairs from each cadaver. Of the knees, 10 underwent transtibial femoral tunnel drilling from a far-medial starting point on the tibia (group 1) and 10 had the femoral tunnel drilled from a medial arthroscopic portal (group 2). The dimensions and size of the apertures, the volume and length of the tunnels, and the distance of the tunnels from the posterior wall and articular surface were measured by computed tomography. RESULTS The mean femoral tunnel length was 29.7 mm in group 1 and 15.7 mm in group 2. The mean volume for each tunnel was 2,401 mm(3) in group 1 and 2,071 mm(3) in group 2. The intra-articular aperture area was 94.6 mm(2) in group 1 and 98.6 mm(2) in group 2. In group 2 the intra-articular shape was more elliptical than in group 1, with the long axis averaging 13.5 ± 1.3 mm (P = .004) and short axis averaging 9.7 ± 1.0 mm (P = .002); in group 2 the long axis averaged 12.5 ± 1.7 and short axis averaged 10.3 ± 0.7 (P = .002). Group 2 was closer to the posterior wall and articular surface (6.9 ± 0.6 mm and 9.4 ± 0.6 mm, respectively) than group 1 (10.8 ± 1.0 mm and 11.8 ± 1.9 mm, respectively). CONCLUSIONS We determined the length and volume of the femoral tunnel to be shorter and smaller, respectively, with a medial arthroscopic portal. In addition, the aperture shape was more of an ellipse with a medial arthroscopic portal. The medial arthroscopic portal also created a femoral tunnel that was closer to the posterior wall and articular surface of the femur. CLINICAL RELEVANCE Improved characterization of osseous tunnels with 3-dimensional figures will allow for improved matching of graft and incorporation.